This is a continuation-in-part of application Ser. No. 477,809 filed June 10, 1974, now U.S. Pat. No. 3,941,375.
This invention relates to paper handling devices and more specifically to paper transporters for use in conjunction with optical character readers.
It is well known in the art to scan a printed page with an optical character reader (OCR) or the like by mechanically transporting the page under a scanning pick-up head. One arrangement utilizes a high-speed shuttle mechanism with reciprocates the page in a tray. Other systems in common use mount the pick-up head on a high speed reciprocating shuttle. Another arrangement, having well-known speed, handling and cost advantages, is to carry the page on a rotating drum. As the page rotates under a scanner, the OCR reads a narrow section or swath of the page which usually corresponds to a single printed line. On successive revolutions, the scanner indexes to read an adjacent swath until the entire page is read.
A paper transporter for use in conjunction with an OCR, including the drum type transporters, must exhibit a number of operating characteristics and capabilities. First, it must stabilize the position and spatial orientation of the paper with respect to a pick-up head or scanner device of the OCR. The paper position is usually secured by belts or wheels acting on the exterior surface of the drum or by a mechanical or vacuum arrangement carried on the drum. Manual placement of the paper or guidance by a reference surface are common methods for aligning the paper on the drum. It is also important that the paper maintain the proper position and alignment during multiple revolutions of the drum. If the proper alignment is not achieved and maintained, the lines of print will not fall in a single reading swath and reading errors will occur. Also, the paper must be controlled without blocking or obscuring any of the printed characters on the sheet.
Another important operating characteristic of a paper transporter for use in conjunction with an OCR is that its operating should be continuous as successive sheets are fed onto and removed from the transporter. For example, many rotating drum transporter systems used in duplicating systems are unsuitable for use in conjunction with OCRs since they require the drum to come to a complete stop each time a new page is placed on the drum. Such transporters typically employ mechanical or vaccuum techniques to secure the paper in the desired position on the drum. Other significant aspects of the continuous operation capability are that the transporter must be relatively free of paper jams, and it must reliably remove the paper from the drum when the scanning is completed, even if the paper adheres to the drum due to the build up of an electrostatic charge. Also, a high speed, continuous operation transporter for OCR applications must be able to accept paper in a variety of conditions, including paper with creases, wrinkles, bent corners, ragged edges and the like, with low likelihood of jamming, and if a jam should occur, it is important to be able to clear the jam quickly and conveniently.
One type of rotating drum transporter utilizes two belts, or sets of belts, that substantially encircle the drum at both of its ends. The belts rotate the drum and simultaneously grip and transport the paper carried on the exterior surface of the drum. It has been found, however, that this arrangement has various disadvantages which severly limit its effectiveness in reading lines of print, and particularly multiple lines of print that extend over substantially the entire surface of a sheet of paper. First, it is difficult to align the paper accurately so that each line of print lies in a plane that is substantially normal to the longitudinal axis of the drum. Second, if a proper alignment is achieved, it is often difficult to maintain this alignment throughout the relatively large number of revolutions required to read a standard typed or printed page. For example, if the paper is initially inserted into the carrier at a slight angle, this alignment can cause the page to advance longitudinally with each revolution. This in turn can cause the scanner to loose synchronization within a line or between lines, read two or more lines in one scan, or completely omit certain lines. Further, even if the paper is inserted correctly, slight differences in the speed, orientation, or tension of a belt located at opposite ends of the drum can cause an objectionable skewing of the paper resulting in the progressive longitudinal shift in the paper's position relative to the drum. Another significant disadvantage of this type of transporter is that it cannot continuously scan the succession of papers since removal of each page requires that the drum come to a complete stop and be manually rotated in a direction reverse to its normal direction of rotation.
Another arrangement which avoids some of the problems associated with the two-belt system utilizes a single belt mounted over a central portion of the rotating drum and substantially encircling the drum except for a relatively small entrance and exit clearance formed between the looped belt ends. This arrangment, however, is unsuitable for reading pages of printed documents since the belt obscures a portion of the print. Another problem is that after a period of operation, the belt tends to accumulate the ink or pencil material forming the printed characters and transfers it to subsequent pages being transported and read.
It is also known in the context of a document alignment station to utilize spring loaded roller assemblies that align a document by sliding it over the exterior surface of a drum against a reference edge. This alignment occurs during a small partial revolution of the drum. Once aligned the force of gravity strips the document from the drum and directs it to an exit chute.
While this document alignment system avoids some of the difficulties inherent in the belt transporters described hereinabove, it does not have the characteristics and capabilities delineated hereinabove required of a high speed transporter for use in conjunction with an OCR. First, it is not designed to carry a document for even one full revolution on the drum. Second, if it could be so used, the document would exit through the exit chute after only one revolution at most. Third, the use of gravity to strip and remove the document from the drum is unreliable at best if an electrostatic charge develops between the document and the drum during the time it is transported.
It is therefore a principal object of this invention to provide a paper transporter for use in conjunction with an OCR that maintains the paper in an accurately predetermined spatial orientation and position with respect to the scanning element of the optical character reader during multiple revolutions of the paper, does not obscure printed characters on the paper and minimizes the development of an attractive static charge between the paper and the transporter.
A further object of this invention is to provide a paper transporter for use in conjunction with an OCR that accepts sheets in an imperfect condition with a minimum likelihood of a paper jam, and facilitates clearance of any jam that does occur.
Another object of this ivention is to provide a paper transporter suitable for continuous high speed operation that reliably directs the paper to an exit means at a preselected time without stopping the transporter or performing manual operatations.
Yet another object is to provide a paper transporter having these advantages and has a relatively low cost of manufacture.